How to Fix Tkinter Error: No Display Name and $DISPLAY Environment Variable?

Tkinter Error: No Display Name and $DISPLAY Environment Variable

The error "_tkinter.TclError: no display name and no $DISPLAY environment variable_" occurs when running a Python script using matplotlib on a server without an X-window system. Xwindows is a graphical user interface (GUI) system required by matplotlib's default Tkinter backend.

Solution:

To resolve this issue, instruct matplotlib to use a backend that is compatible with non-GUI environments. There are several ways to achieve this:

1. Use 'Agg' Backend:

Add the following line to the beginning of your script before importing pyplot:

<code class="python">import matplotlib
matplotlib.use('Agg')</code>

This sets the matplotlib backend to Agg, which is a non-interactive backend suitable for generating images without the need for a graphical display.

2. Set Matplotlib Configuration:

Add the following line to the ~/.config/matplotlib/matplotlibrc configuration file:

backend: Agg

This will instruct matplotlib to use the Agg backend by default for all scripts.

3. Use SSH with X-Forwarding:

When connecting to the server using SSH, use the -X option to enable X-forwarding:

ssh -X remoteMachine

This will allow the script to access the GUI on your local machine.

4. Export DISPLAY Variable:

Export the DISPLAY variable to point to the host machine's IP address and display number:

export DISPLAY=mymachine.com:0.0

More Information:

For more details on using matplotlib in non-interactive environments, refer to the matplotlib FAQ: https://matplotlib.org/faq/howto_faq.html#matplotlib-in-a-web-application-server

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